Image forming apparatus

ABSTRACT

An image forming apparatus, includes: an image forming unit that forms a toner image on a medium; a heating unit that is provided on a downstream side in a transport path from the image forming unit and that is configured to heat a medium being transported in a non-contact manner; a fixing unit that is provided on a downstream side in the transport path from the heating unit and fixes the toner image on the medium; a shielding unit to which force is applied so as to be inform a closed state in which the heating unit is shielded; and an open state forming unit configured to receive power supply to drive the shielding unit so as to form an open state in which the heating unit is opened, and maintain the open state while the power is being supplied.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of International Application No.PCT/JP2020/019871 filed on May 20, 2020, and claims priority fromJapanese Patent Application No. 2019-123948 filed on Jul. 2, 2019.

BACKGROUND Technical Field

The present invention relates to an image forming apparatus.

Related Art

JP-A-2003-076184 describes an image forming apparatus. The image formingapparatus includes a shutter capable of opening and closing an imageforming unit side opening of a fixing unit, and shutter opening positionholding means for holding the shutter at an open position. When theholding by the shutter opening position holding means is released, theshutter moves to a closed position by the own weight thereof regardlessof the electric driving force.

In the image forming apparatus of JP-A-2009-288491, a shielding regionfor shielding radiation from a heating source to a heating region by ashielding portion is changed according to the position of the sheet tobe transported in the heating region.

The fixing device of JP-A-2007-328222 includes a rotating body forheating, an infrared source that is disposed to face the rotating bodyand generates infrared rays, an infrared reflecting member that reflectsinfrared rays to the rotating body side, and a safety element thatdetects an abnormal temperature rise. Further, the fixing deviceincludes a shielding member that moves and shields between the rotatingbody and the infrared source when the rotating drive of the rotatingbody is stopped.

SUMMARY

Aspects of non-limiting embodiments of the present disclosure relate toan image forming apparatus capable of suppressing heating of imageforming means by heating means or fixing means as compared with a casein which non-contact type heating means remain open even when power iscut off.

Aspects of certain non-limiting embodiments of the present disclosureaddress the above advantages and/or other advantages not describedabove. However, aspects of the non-limiting embodiments are not requiredto address the advantages described above, and aspects of thenon-limiting embodiments of the present disclosure may not addressadvantages described above.

According to an aspect of the present invention, there is provided animage forming apparatus, including: an image forming unit that forms atoner image on a medium; a heating unit that is provided on a downstreamside in a transport path from the image forming unit and that isconfigured to heat a medium being transported in a non-contact manner; afixing unit that is provided on a downstream side in the transport pathfrom the heating unit and fixes the toner image on the medium; ashielding unit to which force is applied so as to be inform a closedstate in which the heating unit is shielded; and an open state formingunit configured to receive power supply to drive the shielding unit soas to form an open state in which the heating unit is opened, andmaintain the open state while the power is being supplied.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiment(s) of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a schematic diagram showing a part of an image formingapparatus according to a first exemplary embodiment;

FIG. 2 is a schematic diagram showing a toner image forming unit of theimage forming apparatus according to the first exemplary embodiment;

FIG. 3 is an explanatory view showing a state in which a gripperaccording to the first exemplary embodiment is accommodated in arecessed portion of a counter roller;

FIG. 4 is an explanatory view showing a state in which a medium istransported by a chain gripper according to the first exemplaryembodiment;

FIG. 5 is an enlarged view showing a portion F in FIG. 1;

FIG. 6 is a schematic view showing an open state in which the heatingunit of a second exemplary embodiment is opened, and is a viewcorresponding to the F portion in FIG. 1;

FIG. 7 is a schematic view showing a closed state in which the heatingunit of the second exemplary embodiment is shielded, and is a viewcorresponding to the F portion in FIG. 1;

FIG. 8 is a schematic view showing an open state in which the heatingunit of a third exemplary embodiment is opened, and a view correspondingto the F portion in FIG. 1;

FIG. 9 is a schematic view showing a closed state in which the heatingunit of the third exemplary embodiment is shielded, and is a viewcorresponding to the F portion in FIG. 1;

FIG. 10 is a perspective view of a part showing an open state in whichthe heating unit of the third exemplary embodiment is opened;

FIG. 11 is a perspective view of a part showing a process in which theheating unit of the third exemplary embodiment is shielded;

FIG. 12 is a perspective view of a part showing a closed state in whichthe heating unit of the third exemplary embodiment is shielded;

FIG. 13 is a schematic view showing an open state in which the heatingunit is opened by the opening/closing mechanism according to a fourthexemplary embodiment, and is a view corresponding to the F portion inFIG. 1;

FIG. 14 is a schematic diagram showing a state in which FIG. 13 isviewed from a side;

FIG. 15 is a schematic view showing a closed state in which the heatingunit is shielded by the opening/closing mechanism according to thefourth exemplary embodiment, and is a view corresponding to the Fportion in FIG. 1; and

FIG. 16 is a schematic diagram showing a state in which FIG. 15 isviewed from a side.

DETAILED DESCRIPTION First Exemplary Embodiment

Hereinafter, a first exemplary embodiment of the present invention willbe described with reference to the drawings. FIG. 1 is a schematic viewshowing an image forming apparatus 10 according to the present exemplaryembodiment. The image forming apparatus 10 is an apparatus that forms animage on a medium P such as a sheet.

The image forming apparatus 10 includes an image forming unit 14 thatforms a toner image on a medium P sent from an accommodating unit (notshown) via a feeding-transport unit 12, and a fixing device 16 thatfixes the toner image formed on the medium P by the image forming unit14. The medium P to which the toner image is fixed is discharged from adischarge unit (not shown) via a discharging-transport unit 18. Theimage forming apparatus 10 further includes a transport mechanism 20that transports the medium P between the feeding-transport unit 12 andthe discharging-transport unit 18.

(Image Forming Unit)

The image forming unit 14 has a function of forming a toner image on themedium P. The image forming unit 14 includes a toner image forming unit22 that forms a toner image, and a transfer device 24 that transfers thetoner image formed by the toner image forming unit 22 to the medium P.

<Toner Image Forming Unit>

The toner image forming unit 22 forms a toner image for each color, andincludes toner image forming units 22(Y), 22(M), 22(C), and 22(K) offour colors of yellow (Y), magenta (M), cyan (C), and black (K). Thetoner image forming unit 22 of each color is basically configured in thesame manner except for the toner to be used.

As shown in FIG. 2, the toner image forming unit 22 of each colorincludes a photoconductor drum 30 that rotates in an arrow A direction,and a charging device 32 that charges the photoconductor drum 30. Thetoner image forming unit 22 of each color includes an exposure device 34that exposes the photoconductor drum 30 charged by the charging device32 to form an electrostatic latent image on the photoconductor drum 30.The toner image forming unit 22 of each color further includes adeveloping device 36 that develops the electrostatic latent image formedon the photoconductor drum 30 by the exposure device 34 to form a tonerimage.

<Transfer Device>

As shown in FIG. 1, the transfer device 24 has a function of primarilytransferring toner images of the photoconductor drums 30 of therespective colors onto an intermediate transfer body in a superimposedmanner, and secondarily transferring the superimposed toner images ontothe medium P. The transfer device 24 includes a transfer belt 40 as anintermediate transfer body, a primary transfer roller 42, and a transferunit 44.

The primary transfer roller 42 has a function of transferring the tonerimage formed on the photoconductor drum 30 to the transfer belt 40 at aprimary transfer position T between the photoconductor drum 30 and theprimary transfer roller 42. The transfer belt 40 has an endless shapeand is wound around plural rollers 46.

The transfer belt 40 has a function of transporting the primarilytransferred toner image to a secondary transfer position NT by rotatingin an arrow B direction when at least one of the plural rollers 46 isdriven to rotate.

The transfer unit 44 has a function of transferring the toner imagetransferred to the transfer belt 40 to the medium P. The transfer unit44 includes a secondary transfer unit 48 and a counter roller 50 thatare disposed to face each other. The transfer belt 40 is disposedbetween the secondary transfer unit 48 and the counter roller 50. Arecessed portion 50A configured to accommodate a gripper 68 to bedescribed later is formed on an outer peripheral surface of the counterroller 50.

The transfer unit 44 transfers the toner image transferred to thetransfer belt 40 to the medium P passing through the secondary transferposition NT by electrostatic force generated by the discharging of thesecondary transfer unit 48.

(Transport Mechanism)

The transport mechanism 20 is disposed between the feeding-transportunit 12 and the discharging-transport unit 18. The transport mechanism20 has a function of receiving the medium P from the feeding-transportunit 12 with the chain gripper 60. The transport mechanism 20 has afunction of delivering the received medium P to the discharge-transportunit 18 via the second transfer position NT, the heating unit 62, and afixing unit 64.

<Chain Gripper>

As shown in FIG. 3, the chain gripper 60 includes a pair of endlesschains 66 that are separated from each other and a gripper 68 that isprovided between the two chains 66, and the gripper 68 holds a distalend portion of the medium P on a downstream side D in the mediumtransport direction as shown in FIG. 4.

As shown in FIG. 3, each of the chains 66 is wound around a sprocket 70provided at both ends of the counter roller 50 and sprockets provided atboth ends of a pressure roller 96 described later.

The chain gripper 60 rotates in an arrow C direction when either one ofthe two sprockets 70 is rotated, and transports the medium P held by thegripper 68 through the secondary transfer position NT, the heating unit62, the fixing unit 64, and the discharging-transport unit 18 in thisorder as shown in FIG. 1.

(Fixing Device)

The fixing device 16 has a function of fixing the toner image formed onthe medium P by the image forming unit 14.

The fixing device 16 includes a heating unit 62 provided on thedownstream side D in the medium transport direction of the transportpath H from the image forming unit 14 and configured to heat thetransported medium P in a non-contact manner, and a fixing unit 64provided on the downstream side D in the medium transport direction fromthe heating unit 62 and configured to fix the toner image on the mediumP. A region of the transport path H heated by the heating unit 62 is anupward gradient that increases from the upstream side U in the mediumtransport direction toward the downstream side D in the medium transportdirection.

As shown in FIG. 5, the fixing device 16 includes a restrictingmechanism 80 that restricts release of radiation heat from the heatingunit 62. The restricting mechanism 80 includes a shielding unit 82 towhich force is applied so as to be in a closed state C in which theheating unit 62 is shielded. Further, the restricting mechanism 80includes an open state forming unit 84 that receives power supply todrive the shielding unit 82 to form the open state O in which theheating unit 62 is opened, and maintains the open state O while thepower is being supplied.

As shown in FIG. 1, the fixing device 16 further includes a blowing unit86 that blows air toward a back surface PB of the medium P transportedbetween at least the image forming unit 14 and the heating unit 62. Aguide plate 88 is disposed between the heating unit 62 of the fixingdevice 16 and the image forming unit 14 to guide the air from theblowing unit 86 to the downstream side D in the medium transportdirection.

A lower end portion of the guide plate 88 is bent, and the lower endportion thereof is inclined toward the image forming unit 14 side as itgoes downward, and is disposed on an end portion of a ventilation plate89 described later. The guide plate 88 is made of a metal plate, and theguide plate 88 is made of, for example, an aluminum plate.

<Heating Unit>

The heating unit 62 has a function of melting the toner image of themedium P by heating a surface PA of the medium P transported along thetransport path H by the chain gripper 60 by radiation transmission in anon-contact manner. As shown in FIG. 5, the heating unit 62 includes areflection plate 90, a heating source 92, and a wire mesh 93 (not shown)that covers the heating source 92.

[Reflection Plate]

The reflection plate 90 is formed in a container shape that is opentoward a lower side of the apparatus, and has a function of reflectinginfrared rays from the heating source 92 toward the lower side of theapparatus. The reflection plate 90 is made of a metal plate, and thereflection plate 90 is made of, for example, an aluminum plate.

[Heating Source]

The heating source 92 includes, for example, plural heaters. Examples ofthe heaters of the heating source 92 include a columnar infrared heater.

[Wire Mesh]

The wire mesh 93 partitions the inside and the outside of the reflectionplate 90. The wire mesh 93 suppresses contact between the medium Ptransported by the chain gripper 60 and the heating source 92.

<Blowing Unit>

As shown in FIG. 1, the blowing unit 86 includes a blower 87 and aventilation plate 89.

The blower 87 is disposed inside the chain gripper 60 and below theheating unit 62. The blower 87 blows air to the back surface PB of themedium P transported by the chain gripper 60, and causes the medium P tofloat.

The ventilation plate 89 is disposed between the blower 87 and theheating unit 62 and on the inner peripheral side of the chain gripper60. As shown in FIG. 4, the ventilation plate 89 includes pluralventilation holes 89A through which the air from the blower 87 passestoward the back surface PB of the medium P transported by the chaingripper 60. Accordingly, the medium P transported by the chain gripper60 is caused to float, and the back surface PB of the medium P isbrought into a non-contact state relative to the ventilation plate 89.

Further, as shown in FIG. 1, the ventilation plate 89 extends toward thedownstream side D in the medium transport direction from an end of theheating unit 62 on the upstream side U in the medium transportdirection. In other words, the ventilation plate 89 extends toward theimage forming unit 14 side from the end of the heating unit 62 on theupstream side U in the medium transport direction. Accordingly, the airpassing through the ventilation holes 89A of the ventilation plate 89 isblown toward the back surface PB of the medium P transported between theimage forming unit 14 and the heating unit 62.

<Fixing Unit>

The fixing unit 64 includes a heating roller 94 and a pressure roller96. The fixing unit 64 has a function of fixing the toner image to themedium P by heating and pressurizing the medium P in contact with themedium P.

[Heating Roller]

The heating roller 94 has a built-in heating source, comes into contactwith the surface PA of the medium P transported by the chain gripper 60to heat the medium P, and fixes the toner image to the medium P.

[Pressure Roller]

The pressure roller 96 has a function of pressurizing the medium P bysandwiching the medium P between the pressure roller 96 and the heatingroller 94. A recessed portion 96A configured to accommodate the gripper68 is formed in the outer peripheral surface of the pressure roller 96.

<Restricting Mechanism>

As shown in FIG. 5, the restricting mechanism 80 includes a shieldingunit 82 that shields the heating unit 62, and an open state forming unit84 that opens the shielding unit 82.

[Shielding Unit]

The shielding unit 82 is formed of a plate material having a size thatcovers and shields the heating unit 62, and the shielding unit 82constitutes a single shielding portion. Both side portions of theshielding unit 82 are movably supported by rails 100 extending along thetransport path H.

The rail 100 extends from the heating unit 62 side to the fixing unit 64side, and the shielding unit 82 forms a closed state C in which theshielding unit 82 shields the heating unit 62 when the shielding unit 82moves toward the upstream side U in the medium transport direction alongthe rails 100. Thereby, the release of heat from the heating unit 62 issuppressed. In other words, heat released downward from the heating unit62 is restricted. When the shielding unit 82 moves to the downstreamside D in the medium transport direction along the rails 100, theshielding unit 82 forms an open state O in which the heating unit 62 isopened. As a result, heat is allowed to be released downward from theheating unit 62.

The rail 100 is inclined so as to rise from the upstream side U in themedium transport direction toward the downstream side D in the mediumtransport direction. In other words, the rail 100 is inclined so as torise from the image forming unit 14 side toward the fixing unit 64 side.As a result, force is applied to the shielding unit 82 to move to theupstream side U in the medium transport direction due to the own weightthereof, and force to form the closed state C in which the heating unit62 is shielded is constantly applied to the shielding unit 82.

[Open State Forming Unit]

The open state forming unit 84 is provided on the downstream side D inthe medium transport direction from the heating unit 62. The open stateforming unit 84 includes a winding-up roll 104 that winds up a wire 102extending from downstream side D in the medium transport direction ofthe shielding unit 82 so as to be able to be drawn out, and a motor 106that rotates the winding-up roll 104 in a winding up direction. Further,the open state forming unit 84 includes an electromagnetic clutch 108that connects or disconnects the motor 106 and the rotation mechanism ofthe winding-up roll 104.

The motor 106 receives power supply and rotates the winding roll 104 inthe winding-up direction, thereby driving the shielding unit 82 to thedownstream side D in the medium transport direction to form an openstate O in which the heating unit 62 is opened. The motor 106 suppressesunexpected rotation of the winding-up roll 104 due to the idling torqueof the motor 106.

The electromagnetic clutch 108 connects the motor 106 to the rotationmechanism of the winding-up roll 104 while the electromagnetic clutch108 is powered on, and the rotation of the winding-up roll 104 isregulated by the idle torque (self-locking of the gear) of the motor106.

When the power supply is cut off and the electromagnetic clutch 108 isturned off, the electromagnetic clutch 108 releases the connectionbetween the motor 106 and the rotation mechanism of the winding-up roll104. Therefore, when the power supply is cut off due to a power failureor the like and the electromagnetic clutch 108 is turned off, thewinding-up roll 104 becomes rotatable, and the shielding unit 82 movesto the downstream side D in the medium transport direction due to theown weight thereof, so that the closed state C in which the heating unit62 is shielded is formed.

(Operation and Effects)

The operation of the present exemplary embodiment according to the aboveconfiguration will be described.

As compared with the case in which the heat transfer from thenon-contact type heating unit 62 is continued when the power supply iscut off due to a power failure or the like, it is possible to suppressthe heating of the image forming unit 14 by the heating unit 62 or thefixing unit 64.

In addition, it is possible to suppress the heating of the facingportion such as the blowing unit 86 and the chain gripper 60 facing theheating unit 62.

As a specific example, since the heating unit 62 is shielded by theshielding unit 82, it is possible to suppress the heat of the heatingunit 62 from being transferred to the image forming unit 14. Inaddition, since the distance between the fixing unit 64 and the imageforming unit 14 is long, it is possible to suppress the heat from thefixing unit 64 from being transferred to the image forming unit 14.

A region of the transport path H heated by the heating unit 62 is anupward gradient that increases from the upstream side U in the mediumtransport direction toward the downstream side D in the medium transportdirection. In other words, the region of the transport path H heated bythe heating unit 62 is an upward gradient that increases from the imageforming unit 14 side toward the fixing unit 64 side. Therefore, ascompared with a case in which the region of the transport path H islowered from the upstream side U in the medium transport directiontoward the downstream side D in the medium transport direction, themovement of the air that is warmed and rises is suppressed moving to theupstream side U in the medium transport direction.

The blowing unit 86 blows air toward the back surface PB of the medium Ptransported between the image forming unit 14 and the heating unit 62.Therefore, as compared with the case in which the blowing unit 86 isprovided only in the region facing the heating unit 62, it is possibleto prevent the air warmed by the heating unit 62 from moving toward theimage forming unit 14 side by blowing air from the blowing unit 86.

A guide plate 88 that guides the air from the blowing unit 86 to thedownstream side D in the medium transport direction is disposed betweenthe heating unit 62 and the image forming unit 14. Therefore, ascompared with the case where the guide plate 88 guides the air to theupstream side U in the medium transport direction, it is possible topromote the movement of the air warmed by the heating unit 62 toward theheating unit 62 side.

The shielding unit 82 is composed of a single shielding portion.Therefore, even in the open state O, it is possible to increase theheating efficiency in the open state O as compared with a case in whicha part of the plural shielding portions disposed along the heatingsurface shields the heating portion.

Second Exemplary Embodiment

FIGS. 6 and 7 are views showing a second exemplary embodiment, in whichthe same or equivalent portions as those of the first exemplaryembodiment are denoted by the same reference numerals, descriptionthereof is omitted, and different portions will be described. The secondexemplary embodiment differs from the first exemplary embodiment mainlyin the region of the transport path H heated by the heating unit 62 andthe moving direction of the shielding unit 82.

That is, the region of the transport path H heated by the heating unit62 is formed substantially horizontally, and the rail 100 that guidesthe shielding unit 82 extends substantially horizontally.

The rail 100 extends from the heating unit 2 side to the image formingunit 14 side. As shown in FIG. 6, when the shielding unit 82 moves tothe upstream side U in the medium transport direction along the rail100, the shielding unit 82 forms an open state O in which the heatingunit 62 is opened.

Further, as shown in FIG. 7, when the shielding unit 82 moves to thedownstream side D in the medium transport direction along the rail 100,the shielding unit 82 forms a closed state C in which the heating unit62 is shielded. In this manner, the shielding unit 82 operates in adirection for shielding from a side close to the image forming unit 14to form the closed state C.

One end of a coil spring 110 is fixed to an end face 100A of the rail100 on the upstream side U in the medium transport direction, and theother end of the coil spring 110 is fixed to an end portion of theshielding unit 82 on the upstream side U in the medium transportdirection. As a result, the shielding unit 82 is pulled toward theupstream side U in the medium transport direction by the coil spring110, so that force is constantly applied to the shielding unit 82 so asto be in the closed state C in which the heating unit 62 is shielded.

(Operation and Effects)

In the present exemplary embodiment having the above-describedconfiguration, the same operation and effects as those of the firstexemplary embodiment may be obtained for the same or equivalent portionsas those of the first exemplary embodiment.

In addition, the shielding unit 82 operates in the direction forshielding from a side close to the image forming unit 14 to form theclosed state C. Therefore, as compared with the case of shielding fromthe side close to the fixing unit 64, it may be possible to suppress theheating of the image forming unit 14 by the heat from the heating unit62.

Third Exemplary Embodiment

FIGS. 8 to 12 are views showing a third exemplary embodiment, in whichthe same or equivalent portions as those of the first exemplaryembodiment and the second exemplary embodiment are denoted by the samereference numerals, description thereof is omitted, and differentportions will be described. The third exemplary embodiment differs fromthe above-described exemplary embodiments mainly in the shielding unit82.

That is, as shown in FIGS. 8 and 9, the shielding unit 82 includesplural shielding plates 120 disposed in the length direction of theheating unit 62 along the transport path H. Each of the shielding plates120 is formed in a rectangular shape is long in the width direction ofthe heating unit 62, and a rotation shaft 120A extending in the lengthdirection is provided in the central portion in the width direction.

Each of the shielding plates 120 is rotatably supported by a bracket(not shown) for rotating a rotation shaft 120A, and each of theshielding plates 120 is supported so as to be rotatable about therotation shaft 120A.

As shown in FIGS. 10 to 12, an L-shaped crank portion 122 is formed atan end portion of each rotation shaft 120A, and an operation portion 124protruding laterally is formed at a distal end of the crank portion 122.A rectangular actuation plate 126 extending in the arrangement directionof the shield plates 120 is disposed on an end portion side of each ofthe shielding plates 120. A long hole 128 into which the operationportion 124 of the crank portion 122 of each corresponding shieldingplate 120 is movably inserted is formed in the actuation plate 126.

One end of the coil spring 130 is fixed to an end portion of theoperation plate 126 on the downstream side D in the medium transportdirection, and the other end of the coil spring 130 is fixed to ahousing 132 of the apparatus main body. Accordingly, as shown in FIGS. 9and 12, force is constantly applied to the actuation plate 126 by thecoil spring 130 so that each of the shielding plates 120 of theshielding unit 82 is in the closed state C in which the heating unit 62is shielded.

As shown in FIGS. 8 and 9, a wire 134 extending from the open stateforming unit 84 is fixed to an end portion of the actuation plate 126 onthe upstream side U in the medium transport direction. Accordingly, bywinding up the wire 134 by the winding-up roll 104 of the open stateforming unit 84, as shown in FIGS. 8 and 10, the open state O in whichthe heating unit 62 is opened may be formed and the opening state O maybe maintained.

At this time, each of the shielding plates 120 of the shielding unit 82operates in the direction for shielding from a side close to the imageforming unit 14 to form a closed state.

(Operation and Effects)

In the present exemplary embodiment having the above-describedconfiguration, the same operation and effects as those of the firstexemplary embodiment and the second exemplary embodiment may be obtainedfor the same or equivalent portions as those of the first exemplaryembodiment and the second exemplary embodiment.

In addition, by configuring the shielding unit 82 with the pluralshielding plates 120 disposed at the lower portion of the heating unit62, it is possible to suppress an avoidance space of the shielding unit82 in the open state O as compared with a case in which a singleshielding unit 82 having a size covering the heating unit 62 is used.

Fourth Exemplary Embodiment

FIGS. 13 to 16 are views showing a fourth exemplary embodiment, in whichthe same or equivalent portions as those of the first exemplaryembodiment to the third exemplary embodiment are denoted by the samereference numerals, description thereof will be omitted, and differentportions will be described. The fourth exemplary embodiment differs fromthe above-described exemplary embodiments mainly in the restrictingmechanism 80 that constitutes the open state forming unit.

The restricting mechanism 80 includes a shielding unit 82, and theshielding unit 82 includes a shutter 140 movable along the heating unit62. The restricting mechanism 80 is capable of opening the shutter 140.Further, as shown in FIG. 14, the restricting mechanism 80 includes achanging roller 146 as a changing unit that changes the retractingdirection 142 of the shutter 140 in the open state O to a separatingdirection 144 away from the transport path H, on the upstream side U inthe medium transport direction.

The restricting mechanism 80 includes a folding unit (an upstream sidefirst folding roll 168 and an upstream side second folding roll 174described later) that folds the shutter 140 that moves in the separatingdirection 144 in the approaching direction 148 approaching the transportpath H, and a fixing bar 150 that is a fixing unit that fixes the endportion side of the shutter 140 folded by the folding unit on thetransport path H side with respect to the folding unit. In addition, therestricting mechanism 80 includes a moving unit 152 that moves thefolding unit in the separating direction.

Specifically, as shown in FIG. 13, the restricting mechanism 80 includesa rectangular frame 160 formed to cover the heating unit 62. Both sideedges of an upper portion of the rectangular frame 160 are composed of apair of upper bridge members 162 extending along the transport path H,and the lower portions of the upper bridge members 162 are provided witha pair of middle bridge members 164 extending along the transport pathH.

A changing roll 146 that is a changing unit is rotatably supported onthe upstream side U in the medium transport direction between the middlebridge members 164.

The shutter 140, of which the retracting direction 142 is changed to theseparating direction 144 by the changing roller 146, is folded backtoward the approaching direction 148 by the upstream side first foldingroll 168 that is the upstream side first folding unit between theupstream side extension brackets 166 extending from the moving unit 152.

The shutter 140 folded back by the upstream side first folding roll 168is folded back toward the separating direction 144 by the upstream sidefolding roll 172 between the upstream side rising brackets 170 extendingfrom the middle bridge members 164 of the rectangular frame 160. Notethat the upstream side folding roll 172 and the upstream side secondfolding roll 174 described later may not be provided.

The shutter 140 folded back by the upstream side folding roll 172 isfolded back toward the approaching direction 148 by the upstream sidesecond folding roll 174 that is the upstream side second folding unitbetween the upstream side extension brackets 166.

One end of the shutter 140 folded back by the upstream side secondfolding roll 174 is fixed to the fixing bar 150 that is a fixing unitbetween the upstream side rising brackets 170.

As shown in FIGS. 15 and 16, the restricting mechanism 80 includes achanging roller 182 that changes a tensile direction 180 of the shutter140 in the closing operation to a separating direction 144 away from thetransport path H. The changing roller 182 is provided on the downstreamside D in the medium transport direction of each middle bridge member164.

The shutter 140 in which the tensile direction 180 is changed to theseparating direction 144 by the changing roller 182 is folded backtoward the approaching direction 148 approaching the transport path H bythe downstream side first folding roll 186 between the downstream sideextension brackets 184 extending from the moving unit 152.

The shutter 140 folded back by the downstream side first folding roll186 is folded back toward the separating direction 144 by a downstreamside folding roll 190 between the downstream side rising brackets 188extending from the respective middle bridge members 164 of therectangular frame 160.

The shutter 140 folded back by the downstream side folding roll 190 isfolded back toward the approaching direction 148 by a downstream sidesecond folding roll 192 between the downstream side extension brackets184.

The other end of the shutter 140 folded back by the downstream sidesecond folding roll 192 is fixed to a fixing bar 194 extending betweenthe two downstream side rising brackets 188.

The shutter 140 is formed in a long sheet shape, and as shown in FIGS.15 and 16, forms a closed state C in which the heating unit 62 isshielded. A rectangular opening portion 140A (see FIG. 15) is formed inan intermediate portion of the shutter 140, and by disposing the openingportion 140A in a lower portion of the heating unit 62, as shown inFIGS. 13 and 14, an open state O in which the heating unit 62 is openedis formed.

Support members 200 are provided on both upper bridge members 162 of therectangular frame 160, and a rectangular frame shaped moving unit 152 issupported on a rotation shaft 202A of the clutch motor 202 extendingfrom the support member 200.

Rotation force is applied to the rotation shaft 202A by, for example, aspiral spring, and force is applied such that the moving unit 152rotates in a direction in which the shutter 140 forms a closed state Cin which the heating unit 62 is shielded.

Note that, by adjusting the center of gravity of the moving unit 152,the moving unit 152 may be configured to rotate by the own weightthereof in the direction in which the closed state C is formed.

The clutch motor 202 rotates the moving unit 152 when receiving powersupply, and as shown in FIGS. 13 and 14, the upstream side U in themedium transport direction of the moving unit 152 is raised and therising state is maintained by the idling torque of the motor 202 withthe clutch.

Accordingly, a shutter portion including the opening 140A moved to thedownstream side D in the medium transport direction of the moving unit152 is moved to the lower portion of the heating unit 62. At the sametime, the shutter portion shielding the heating unit 62 is retracted tothe upstream side U in the medium transport direction of the moving unit152, and the open state O is maintained.

When the power supply is cut off due to a power failure or the like andthe clutch of the motor 202 with the clutch is turned off, as shown inFIGS. 15 and 16, the upstream side U in the medium transport directionof the moving unit 152 is lowered. Then, the shutter portion retractedto the upstream side U in the medium transport direction of the movingunit 152 is drawn out to the lower portion of the heating unit 62. Atthe same time, the shutter portion including the opening portion 140Adisposed in the lower portion of the heating unit 62 is moved to thedownstream side D in the medium transport direction of the moving unit152, and the closed state C is formed.

(Operation and Effects)

In the present exemplary embodiment having the above-describedconfiguration, the same operation and effects as those of the firstexemplary embodiment to the third exemplary embodiment may be obtainedfor the same or equivalent portions as those of the first exemplaryembodiment to the third exemplary embodiment.

Further, in the present exemplary embodiment, the changing roll 146 isprovided as a changing unit that changes the retracting direction 142 ofthe shutter 140 in the open state O to the separating direction 144 awayfrom the transport path H. Therefore, as compared with the case in whichthe retracting direction 142 of the shutter 140 is set along thetransport path H, it is possible to suppress the dimension of thestandby space of the shutter 140 along the transport path H.

The restricting mechanism 80 includes each folding roll 168, 174 thatfolds the shutter 140 that moves in the separating direction 144 in theapproaching direction 148, and a fixing bar 150 that is a fixing unitthat fixes the end portion side of the shutter 140 folded by the foldingrolls 168, 174. The restricting mechanism 80 also includes a moving unit152 that moves each of the folding rollers 168, 174 in the separatingdirection 144. Therefore, it is possible to suppress the dimension ofthe standby space of the shutter 140 in the direction away from thetransport path H as compared with the case in which the folding unit isnot provided to fold the shutter 140 moving in the separating direction144.

In each of the exemplary embodiments described above, the case in whichthe region of the transport path H heated by the heating unit 62 is theupward gradient or the horizontal from the upstream side U in the mediumtransport direction toward the downstream side D in the medium transportdirection has been described, but the present disclosure is not limitedthereto. For example, the region of the transport path H heated by theheating unit 62 may have a downward gradient or may extend in thevertical direction from the upstream side U in the medium transportdirection toward the downstream side D in the medium transportdirection.

The blower 87 and the ventilation plate 89 may not be provided.

The shielding unit 82 does not necessarily need to shield the wire mesh93 as long as the shielding unit 82 shields the heating source 92.However, as shown in FIG. 5, in the first exemplary embodiment, theshielding unit 102 forms a closed state in which the heating source 92and the wire mesh 93 are shielded. Accordingly, in the closed state, thewire mesh 93 heated by the heating source 92 is not exposed. Therefore,workability when the operator performs some work in the vicinity of thechain gripper 60, such as when the operator removes the paper when paperjam occurs, is improved. Further, in the closed state, it is desirablethat the dimensions of the shielding unit 82 in the medium transportdirection, and the dimension in the direction in which the heatingsource 92 and the chain gripper 60 face each other and in the directionintersecting the medium transport direction are both larger than thoseof the wire mesh 93. This is because the wire mesh 93 may be completelyshielded in the closed state. In addition, in FIG. 5, the wire mesh 93is disposed in an inner space, surrounded by the reflecting plate 90,with respect to a position of the reflecting plate 90 that is opentoward the lower side of the device. Accordingly, the shielding unit 82is more likely to shield the wire mesh 93 than in the case in which thewire mesh 93 is disposed below the position opened toward the lower sideof the device.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theexemplary embodiments were chosen and described in order to best explainthe principles of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. An image forming apparatus, comprising: an imageforming unit that forms a toner image on a medium; a heating unit thatis provided on a downstream side in a transport path from the imageforming unit and that is configured to heat a medium being transportedin a non-contact manner; a fixing unit that is provided on a downstreamside in the transport path from the heating unit and fixes the tonerimage on the medium; a shielding unit to which force is applied so as toform a closed state in which the heating unit is shielded; and an openstate forming unit configured to receive power supply to drive theshielding unit so as to form an open state in which the heating unit isopened, and maintain the open state while the power is being supplied.2. The image forming apparatus according to claim 1, wherein a region ofthe transport path heated by the heating unit has an upward gradientfrom an upstream side to a downstream side.
 3. The image formingapparatus according to claim 1, further comprising a blowing unit thatblows air toward a back surface of a medium being transported betweenthe image forming unit and the heating unit.
 4. The image formingapparatus according to claim 2, further comprising a blowing unit thatblows air toward a back surface of a medium being transported betweenthe image forming unit and the heating unit.
 5. The image formingapparatus according to claim 3, further comprising a guide plate that isdisposed between the heating unit and the image forming unit and that isconfigured to guide air from the blowing unit to a downstream side. 6.The image forming apparatus according to claim 4, further comprising aguide plate that is disposed between the heating unit and the imageforming unit and that is configured to guide air from the blowing unitto a downstream side.
 7. The image forming apparatus according to claim1, wherein the shielding unit is operated from a side close to the imageforming unit in a direction for shielding so as to form the closedstate.
 8. The image forming apparatus according to claim 2, wherein theshielding unit is operated from a side close to the image forming unitin a direction for shielding so as to form the closed state.
 9. Theimage forming apparatus according to claim 3, wherein the shielding unitis operated from a side close to the image forming unit in a directionfor shielding so as to form the closed state.
 10. The image formingapparatus according to claim 4, wherein the shielding unit is operatedfrom a side close to the image forming unit in a direction for shieldingso as to form the closed state.
 11. The image forming apparatusaccording to claim 5, wherein the shielding unit is operated from a sideclose to the image forming unit in a direction for shielding so as toform the closed state.
 12. The image forming apparatus according toclaim 6, wherein the shielding unit is operated from a side close to theimage forming unit in a direction for shielding so as to form the closedstate.
 13. The image forming apparatus according to claim 7, wherein theshielding unit includes a single shielding portion.
 14. The imageforming apparatus according to claim 8, wherein the shielding unitincludes a single shielding portion.
 15. The image forming apparatusaccording to claim 9, wherein the shielding unit includes a singleshielding portion.
 16. The image forming apparatus according to claim10, wherein the shielding unit includes a single shielding portion. 17.The image forming apparatus according to claim 11, wherein the shieldingunit includes a single shielding portion.
 18. The image formingapparatus according to claim 12, wherein the shielding unit includes asingle shielding portion.
 19. The image forming apparatus according toclaim 1, wherein the shielding unit includes a shutter movable along theheating unit, and the image forming apparatus further comprises achanging unit configured to change a retracting direction of the shutterin the open state to a separating direction away from the transportpath.
 20. The image forming apparatus according to claim 19, wherein theopening state forming unit includes a folding unit that folds theshutter moving in the separating direction in an approaching directionapproaching the transport path, a fixing unit that fixes an end portionside of the shutter folded by the folding unit on a side of thetransport path with respect to the folding unit, and a moving unit thatmoves the folding unit in the separating direction.